JSON Patch Lab is part of DevStudio — a free, in-browser collection of developer utilities that work without sign-up, installation, or any backend service. Apply RFC 6902 patches with a step-by-step trace, derive RFC 6902 + RFC 7396 merge patches between two documents, and validate patches offline + dry-run, all running entirely on your device. Because the page never uploads what you paste, you can run sensitive payloads, configuration files, secrets, or production data through it with confidence: nothing leaves your browser tab. Use JSON Patch Lab for ad-hoc debugging, code review, log triage, release prep, learning a new format, or as a quick scratchpad while you build. If you use this tool a lot, pair it with JSON Codegen, Data Converter, Misc Converters, and the rest of the DevStudio toolkit for related developer workflows.